var stringifyPrimitive = function(v) {
    switch (typeof v) {
        case 'string':
            return v;
        case 'boolean':
            return v ? 'true' : 'false';
        case 'number':
            return isFinite(v) ? v : '';
        default:
            return '';
    }
};

/**
 * Changes XML DOM to JSON  （xml 不带属性）
 * @param xml
 * @returns {{}}  js对象
 */
 var xmlToJson = function(xml){
    // Create the return object
    var obj = {};
    if(!xml){
        return obj;
    }
    if (xml.nodeType == Node.TEXT_NODE) { // text
        obj = xml.nodeValue;
    }

    // do children
    if (xml.hasChildNodes()) {
        for(var i = 0; i < xml.childNodes.length; i++) {
            var item = xml.childNodes.item(i);
            var nodeName = item.nodeName;
            if (typeof(obj[nodeName]) == "undefined") {
                if( nodeName === '#text'){
                    // 待优化。。。。Error情况下返回的responseXml数据带\n冗余字符 会解析错误
                    if(item.nodeValue.indexOf('\n') == -1){
                        obj = item.nodeValue;
                    }
                }else{
                    obj[nodeName] = xmlToJson(item);
                }
            } else {//同级同标签转化为数组
                if (typeof(obj[nodeName].length) == "undefined") {
                    var old = obj[nodeName];
                    obj[nodeName] = [];
                    obj[nodeName].push(old);
                }
                obj[nodeName].push(xmlToJson(item));
            }
        }
    }
    return obj;
};

var queryStringify = function(obj, sep, eq, name) {
    sep = sep || '&';
    eq = eq || '=';
    if (obj === null) {
        obj = undefined;
    }
    if (typeof obj === 'object') {
        return Object.keys(obj).map(function(k) {
            var ks = encodeURIComponent(stringifyPrimitive(k)) + eq;
            if(!obj[k]){
                return '';
            }
            if (Array.isArray(obj[k])) {
                return obj[k].map(function(v) {
                    return ks + encodeURIComponent(stringifyPrimitive(v));
                }).join(sep);
            } else {
                return ks + encodeURIComponent(stringifyPrimitive(obj[k]));
            }
        }).filter(Boolean).join(sep);

    }
    if (!name) return '';
    return encodeURIComponent(stringifyPrimitive(name)) + eq +
        encodeURIComponent(stringifyPrimitive(obj));
};

var xhrRes = function (err, xhr, body) {
    var headers = {};
    const responseHeaders = xhr.getAllResponseHeaders()
    if (typeof responseHeaders === 'string') {
        responseHeaders.trim().split('\n').forEach(function (item) {
            if (item) {
                var index = item.indexOf(':');
                var key = item.substr(0, index).trim().toLowerCase();
                var val = item.substr(index + 1).trim();
                headers[key] = val;
            }
        });
    }
    
    return {
        error: err,
        statusCode: xhr.status,
        statusMessage: xhr.statusText,
        headers: headers,
        body: body,
    };
};

var xhrBody = function (xhr, dataType) {
    return !dataType && dataType === 'text' ? xhr.responseText : xhr.response;
};

var request = function (opt, callback) {
    return new Promise((resolve, reject) => {
        // method
        var method = (opt.method || 'GET').toUpperCase();

        // url、qs
        var url = opt.url;
        if (opt.qs) {
            var qsStr = queryStringify(opt.qs);
            if (qsStr) {
                url += (url.indexOf('?') === -1 ? '?' : '&') + qsStr;
            }
        }

        // 创建 ajax 实例
        var xhr = new XMLHttpRequest();
        xhr.open(method, url, true);
        // xhr.responseType = opt.dataType || 'text';

        // 处理 xhrFields 属性
        // if (opt.xhrFields) {
        //     for (var xhrField in opt.xhrFields) {
        //         xhr[xhrField] = opt.xhrFields[xhrField]
        //     }
        // }

        // 处理 headers
        var headers = opt.headers;
        if (headers) {
            for (var key in headers) {
                if (headers.hasOwnProperty(key) &&
                    key.toLowerCase() !== 'content-length' &&
                    key.toLowerCase() !== 'user-agent' &&
                    key.toLowerCase() !== 'origin' &&
                    key.toLowerCase() !== 'host') {
                    xhr.setRequestHeader(key, headers[key]);
                }
            }
        }

        // onprogress
        if (opt.onProgress && xhr.upload) xhr.upload.onprogress = opt.onProgress;
        if (opt.onDownloadProgress) xhr.onprogress = opt.onDownloadProgress;

        // timeout
        if (opt.timeout) xhr.timeout = opt.timeout;
        xhr.ontimeout = function(event){
            var error = new Error('timeout');
            resolve.call(null, xhrRes(error, xhr));
        };

        // success 2xx/3xx/4xx
        xhr.onload = function () {
            console.log('xhr.responseXML:', JSON.stringify(xhr));
            if(xhr.status === 404){
                resolve.call(null, xhrRes(xhr.statusText, xhr, null));
                return;
            }
            if(xhr.status < 500 && xhr.status > 400){
                var err = xhr.responseXML ? xmlToJson(xhr.responseXML) : '';
                resolve.call(null, xhrRes(xhr.responseXML ? err : '', xhr, null));
                return;
            }
            let res = ''
            if (xhr.responseType) {
                res = this.response
            } else {
                res = xhr.responseXML ? xmlToJson(xhr.responseXML) : ''
            }
            resolve.call(null, xhrRes(null, xhr, res));
        };

        // error 5xx/0 (网络错误、跨域报错、Https connect-src 限制的报错时 statusCode 为 0)
        xhr.onerror = function (err) {
            var body = xhrBody(xhr, opt.dataType);
            if (body) { // 5xx
                resolve.call(null, xhrRes(null, xhr, body));
            } else { // 0
                var error = xhr.statusText;
                if (!error && xhr.status === 0) error = {Error: 'CORS blocked or network error'}
                resolve.call(null, xhrRes(error, xhr, body));
                throw new Error('CORS blocked or network error');
            }
        };

        if (opt.responseType) {
            xhr.responseType = opt.responseType
        }
        // send
        xhr.send(opt.body || null);
        
    // 返回 ajax 实例，用于外部调用 xhr.abort
    // return xhr;
    })

};

// 发起请求 通用前置处理
var generalRequest = function(params, cb){
    var method = params.method || 'GET';
    var url = params.Url || params.url;
    var body = params.body;
    var opt = {
        method: method,
        url: url,
        headers: params.headers,
        qs: params.qs,
        body: body,
        date: params.date,
        onProgress: params.onProgress,
        responseType: params.responseType
    };
    if (this.config.securityToken) {
        opt.headers['X-Ksc-Security-Token'] = this.config.securityToken
    }
    if (method === 'POST') {
        // opt.headers[''] = '*'
    }
    if(this.config.timeout) {
        opt.timeout = this.config.timeout;
    }
   
    return request(opt);
   
}

module.exports = generalRequest;
